DE2105643A1 - METHOD AND DEVICE FOR THE ELECTROCHEMICAL PRODUCTION OF HYDROGEN FROM WATER VAPOR AND NITROGEN FROM AIR - Google Patents

Description

Method and device for the electro-chemical production of hydrogen from water vapor and nitrogen from air The invention relates to a method and a device for the production of hydrogen from water vapor and nitrogen from air with galvanic solid electrolyte cells. Me the application of the invention chemical plants that synthesize ammonia and hydrogen are particularly suitable as well as nitrogen or inert Sohutz- or purge gases.

For the production of hydrogen for synthesis and other purposes A number of procedures have long been known to those of recent times Production of hydrogen by electro-chemical separation of oxygen heated water vapor has been added in solid electrolyte cells. With the new electroohemisohen process uses electrical energy in cells with oxygen ion-conducting solid electrolytes cathodisohydrate reduced and anodisohoxy releases oxygen or oxidizes a flammable gas that has passed by. The process has the advantage that it immediately provides very pure hydrogen.

In order to win Ammoniaksythesegaß, is provided, parallel to the hydrogen production To liquefy air in the known quietly and to break it down by distillation. But it was also proposed in solid electrolyte cells using electrical energy to separate oxygen from air, with the remaining 3 constituents, i.e. predominantly Nitrogen, left behind.

For hydrogen and nitrogen production with solid electrolyte cells you need large amounts of electrical energy, in the form of strong direct currents.

The degree of efficiency of power generation and power line losses play a role therefore an essential role in operating costs. The decomposition of water vapor in Solid electrolyte cells with anodic fuel gas oxidation and supply of electrical energy does not appear to be economically much more advantageous than known processes for producing hydrogen duroh steam reforming clay hydrocarbons, as also the fuel gas for operation the solid electrolyte cells must be processed.

The present invention now aims at the production of hydrogen from water vapor and nitrogen from air with the help of solid electrolyte cells design that there are clear economic advantages over known processes result.

The invention is based on the task of producing hydrogen and nitrogen in solid electrolyte cells closely with highly effective methods of obtaining electrons To connect direct current, so that a high overall efficiency with the lowest possible Cost of materials results, this object is achieved by the invention Combination of energy-consuming solid electrolyte cells made from water vapor Separate oxygen with energy-supplying solid electrolyte cells, which are used as fuel cells working to convert atmospheric oxygen with a flammable gas and nitrogen as a residual component deliver.

As is known, solid electrolyte fuel cells become large aggregates together, whereby they then themselves at the required high operating temperature from about 600 to 1300 ° C Since such aggregates with an efficiency work at 60%, the combination of separate facilities is already worthwhile Solid electrolyte cells - on the one hand for energy generation and on the other hand for Water vapor decomposition - to the unit according to the invention.

However, the solid electrolyte cells are largely used for water vapor decomposition with those for energy production and, if desired, also nitrogen production according to the invention in a closed facility in a small space electrically as well if possible also interconnected with regard to the combustion gas space. Become one part several solid electrolyte fuel cells and, on the other hand, also several solid electrolyte cells connected to tubular cell aggregates for the steam decomposition and the as tubes parallel next to one another or one inside the other cell aggregates like this connected in series so that an electrical circulating current arises from the water vapor space and oxygen electrochemically from the air space into the common combustion gas space convicted.

As has been found, the gas yield, i.e. H.

the molar amount of hydrogen and nitrogen that can be obtained per mole of fuel gas as well as the production density, d. H.

the amount of hydrogen and nitrogen that can be obtained per unit volume of the system, with the numerical ratio of the electrolysis and fuel cells held together ß = zE / e.g. change, as a first approximation applies to the gas yields (fuel gas CO; n- amount of substance in mol) and for the production densities Here, EB denotes the mean emf of the fuel cells, EE the mean emf of the cells for water vapor decomposition, PB and PE the mean polarization voltages, RF the mean wind position and VF the mean volume (aggregate volume / number of cells) of a single solid electrolyte cell.

ß (EE - PE) is small compared to (EB - PB). Therefore the production densities essentially depend on the factors PJ (ß + 1) 2 and 1 / (ß + t) 2 on ß and differ for hydrogen and nitrogen by the production constants As FIGS. 1 and 2 show, a high gas yield is not associated with a high production density and there is a very different curve for the two parameters. With the == 5.6 matched to the ammonia synthesis, only 52% of the maximum possible hydrogen production is obtained.

In contrast, hydrogen production is achieved at maximum density (ß 3 1) only a gas yield of 50%.

According to the invention, a circuit quotient zE / is, for example, between 1 and 5.6 chosen in such a way that as a compromise between fuel use (gas yield) and plant use (production dowte) the optimal economic effect arises.

The value D = 3, for example, appears to be favorable. H. the interconnection of the fuel cells each with three times the amount of solid electrolyte cells for the decomposition of water vapor.

In this case, 75% of the maximum possible density of hydrogen production will be obtained and the gas yield is H2 = 0.75 and N2 r 0.47 in the ammonia synthesis about half of the nitrogen obtained remains and can be used elsewhere will.

Solid electrolytes are becoming better known in the device according to the invention Kind of zirconium oxide with any content of hafnium oxide and with single or mixed ones Additions of magnesium, calcium, scandium, yttrium oxide or oxides of lanthanides, preferably from a mixture of 82 mol% ZrO2, 10 mol% PO, and 8 mol -MgO, used and if necessary with sintering aids such as aluminum, beryllium or iron oxide processed into dense ceramics. The electrodes are known to exist so far they come into contact with reducing gases, made of porous layers of nickel, Copper, iron, cobalt or any other, under the selected operating conditions stable pure, mixed or alloyed metal phase with, if necessary, for reduction Auxiliaries such as zirconium oxide mixed in with sintering.

To reduce the polarization on the electrodes under reducing gas and the adjustment of the water gas fatigue weight to catalyze it is according to the invention An additive of 5 - 50% by weight or an intermediate mixture is mixed into the electrode material brought from the corresponding substance between the solid electrolyte and the electrode, and Although consisting of cerium, chromium or uranium oxide with a solid electrolyte component, preferably from 30 to 80 31 -% chromium, cerium or uranium oxide plus 10 to 55 mol-f zirconium oxide plus 10 to 15 mole percent yttria. As far as they are exposed to oxidizing gas the electrodes made of well-known, highly conductive oxidic material such as strontium lanthanum or praseodymium cobaltate or in each case with or without additives such as aluminum oxide for Improvement of sintering and adhesive properties formed.

Do not trap the cell series by already known methods of series connection Clay solid electrolyte cells are joined together, are the connections between the individual cells as well as between cell series on different fixed electrolx tubes according to the invention with the help of duroh the solid electrolyte wall guided and therein with a Glass gasdioht fused metal wires, mixed metal-ceramic bodies or Ceramic pins made of electronically conductive material for the electrodes under oxidizing Gas called type to produce.

Will different fuel and electrolyte cell series be the same gas reserves charged, so can as a result of different flow resistances between these cell series there are noticeable differences in the degree of conversion of the gases and in performance occur. A compensation of the operating data is except raw yarlation of flow resistances (Bltndeq) according to the invention created by the fact that Eadpcle of the same kind for groups of series of fuel and electrolyte cells which connects the fuel cell series to one another in an electrically conductive manner.

From the connected end poles of the groups of cell series one can according to the invention also lead out electrical lines from the unit to over these lines also feed electrical energy or electrical energy refer to. In this way, the heat balance of the system can be influenced and the production diameters vary.

If coal or hydrocarbons are used as fuel, this fuel is included according to the invention in a in the gas generator Reaction room with part of the anodes of the fuel and electrolysis cells outflowing, more or less oxidized fuel gas and with heat from the cell units converted to fresh fuel gas.

Part of the anode gas therefore goes through a cycle.

In the solid electrolyte cells it is oxidized in the fuel reactor endothermic reaction regenerates and after the necessary cleaning the cells again fed. As the number of moles in the fuel reactor increases, will oxidized fuel gas directly from the cell units or from downstream separate ones Fuel cells or combustion systems that use the combustion of the exhaust gas complete fed to the chimney. If there is excess heat in the system an excess of fuel gas can also be produced and used for other purposes discharge into the gas network.

The continuous operation of the gas generator according to the invention requires the regulation of various parameters.

The system keeps itself through the accumulating in the fuel cells reversible reaction heat as well as due to the internal resistance of all solid electrolyte cells accruing JOULEsohe heat at operating temperatures between 600 and 13000 C. That neither cooling nor overheating can occur, among other things due to the flow of fuel gas be managed.

This gas flow is to be adjusted so that the conversion in the plant just as much heat is generated as through exchange with the environment (radiation, Consumption in reactors or evaporators) is lost. The regulation takes place with With the help of a temperature sensor, the fuel gas flow over known devices throttles when the temperature of the system rises and increases when the temperature falls. The temperature signal is graded in a corresponding manner and in an expedient manner Also for the regulation of other named operating parameters that influence the heat balance used.

The water vapor flow through the electrolytic cells is according to the invention to be regulated so that there is always an excess of water vapor at the end of the cells is.

This excess increases the total voltage in the conductor circuit and thus the power or production radio, but it can also be used as a coolant can be used to control the temperature of the system. From the produced H2 / H2O mixture the water vapor in the required Iß is condensed in heat exchangers and if necessary with Trookenmitte or electrochemically in downstream solid electrolyte cells with regulated electrolysis voltage removed.

In steel pipes that are built into the interior or the building of the system can, as far as the heat retention allows, water vapor can be produced from water and become overheated.

The required air is according to the invention with its natural moisture content, with additional moistening at normal temperature or with water vapor additives Orification used to. If the airflow is completely dry and too weak, it could be after Separation of all oxygen in the last cells of a cell series, in which is only present after nitrogen at the cathode, due to the electromotive force of the remaining cells, the solid electrolyte will decompose. If you are present of water vapor begins to decompose after separation of the atmospheric oxygen of the water steamer without attack by the electrolyte, Talls at the end of the cell series the water vapor decomposition begins, so the air flow is too weak, the falls The total voltage of this fuel cell series is regulated as a signal, namely air flow regulated according to the invention with the total voltage of the fuel cell series as a signal, in such a way that as little or no oxygen as possible remains in the gas stream.

The air flow is regulated for entire groups of cell series with the help of the voltage between the compounds according to the invention more similar End roll of fuel cell series.

Any small residual oxygen in the nitrogen flow from the fuel cells are, as far as they interfere with the use of nitrogen, by metering the for the conversion to water vapor necessary amount of hydrogen or by electrochemical Withdrawal in subsequent solid electrolyte cells with constant electrolysis voltage removed measuring sensors in the form of solid electrolyte cells for gas analysis control signals deliver.

In addition to the noble gases, there is also carbon dioxide in the nitrogen obtained in the air, which partially converts with hydrogen to carbon monoxide.

If the low content is a problem, it must be done before or after passing the plant a separation can be carried out by known methods.

In order to keep the gas turnover under control and to regulate the system, According to the invention, the electromotive forces are applied to separate solid electrolyte cells on the solid electrolyte pipes, in the gas pipes, in pipe connections or behind Gas sampling probes measured, in particular that entering the fuel cells Fuel gas, the more or less oxidized fuel gas, ss resulting 1; hydrogen / steam mixture and the emerging nitrogen are of interest.

reliable signals for regulation as well as for potentiometric determination the gas composition is preferably obtained with air at the reference electrode Measuring cells.

Systems of the type according to the invention provide closed elements d: to which a fuel as well as water and air are supplied and those next to that are not usable exhaust gas come off hydrogen and nitrogen. You stand out from familiar ones Electrolysis systems are characterized by the fact that they are high-efficiency direct current generators even included. Compared to the well-known Wasserelektroijse there is no need for a power station as well as power transmission and wall facilities.

With regard to the ammonia synthesis, separate plants are also not required for nitrogen production, since the systems according to the invention themselves nitrogen in excess deliver. Hydrogen and nitrogen are in high purity at a minimum Material and energy consumption in a continuous, in various ways in its effect and performance gain controllable procedures.

The invention is to be described in more detail below using an exemplary embodiment are explained without the variety of possible on the basis of the solution according to the invention Embodiments wanting to narrow it down. In the accompanying drawings show: 1: the dependence of the gas yield on the ratio of the number of electrolysis cells for the number of fuel cells, FIG. 2: the dependence of the production constant the ratio of the number of electrolysis cells to the number of fuel cells, Fig. 3: Partial cross-section, partial view and diagram of a system module, Fig. 4: the top view of a system module, Fig. 5: the circuit diagram for groups of 10 fuel and 30 electrolysis cells, FIG. 6: the cross-section through ellen plant module and the adjacent space with reaction chamber, Fig. 7: the plan view of an annular arrangement of 20 modules.

On the basis of those shown in FIGS. 1 and 2, which have already been explained Relationships is three times the number in the training example of the fuel cells Assigned to electrolytic cells.

FIG. 3 shows the cross section through a solid electrolyte tube closed on one side with fuel cells held in series, with nitrogen from the inside sucked in and air is sucked in from the outside, the cross section through a one-sided closed solid electrolyte tube with series-connected electrolysis cells those inside, hydrogen sucked from the end and water vapor from a gap is nachgesucht, and the view of a second such solid electrolyte tube with electrolysis cells connected in Selie, the Yerso holding of the anodes on the Outer and Ka.thoden on the inner wall of the solid electrolyte tubes via holes due to the solid electrolyte is evident from the cross-sectional drawings. To the group of solid electrolyte tubes, the cells of which are all connected together to form a series belongs to a fourth pipe, which is in front of the one drawn in the view and is not shown. The plan of such groups is shown in FIG. 4 and from Figure 5 shows the electrical circuit; the circuit diagram also shows electrical Connections between the individual groups for power balancing and signaling to the outside and, if necessary, for energy supply or

For example, 150 of these groups will be in one of the Modules housed from which larger systems are built, all solid electrolyte tubes of a module are in a common combustion gas space, into which fresh Fuel gas flows in and out of the consumed fuel gas below through a gap emerges laterally.

part of this used fuel gas is released into the chimney, the remaining gas forms new fuel gas with the addition of fuel and heat, the is fed to the cells after cleaning.

In Figure 6 is shown how in a circular arrangement of the The type shown in Figure 7 in close thermal contact between the modules, the reaction chambers for the production of the fuel gas as well as lines and heat exchangers are. The central free space of the circuit arrangement accommodates gas cleaning facilities on.

Several layers of 20 modules each built on top of each other lead to tower-like structures Gas generators, from which the products hydrogen and nitrogen are put into manifolds, as shown in Figure 4, pulls out for processing. Because free oxygen only comes through Ceramic pipes flows, the gas containers can largely be made of metallic materials getting produced. The outer skin of the system encloses the one visible in FIGS. 3 and 6 Thermal insulation layer located in water vapor. Other necessary Isolation layers have been omitted from the drawings. Every single module the system is accessible from the outside, so that the sensors for control are convenient and in the event of malfunctions, changes, repairs, cancellations and replacements have it done.

Claims (9)

Claims 1. Process for the electrochemical production of hydrogen Water vapor and nitrogen from air, characterized in that solid electrolyte cells that separate oxygen from water vapor, with solid electrolyte cells that React atmospheric oxygen with a flammable gas and nitrogen as a residual component deliver, have been combined, preferably in such a way that in one closed Provision in confined spaces, series of solid electrolyte cells for water vapor resp. Air separation are arranged parallel to each other or in an anchoring, where in these circuits the ratio of the number of water vapor cells to the number of the air cells is between 1 and 5 to 6. 2. The method according to claim 1, characterized in that the for the The anodes of the two types of solid electrolyte cells require fuel gas in a reaction space inside the plant from sole or hydrocarbons with heat and more or less oxidized fuel gas is produced from the solid electrolyte cells and thus a Part of the anode gas Jewils is sent in a circle through the plant. 3. The method according to claim 1 and 2, characterized in that the Heat balance of the system by the amount of fuel gas supplied, the amount of primary fuel reacted with oxidized fuel gas, the amount of that passed through Excess water vapor, the amount of water vapor produced in parallel from water, the amount of over the electrical supply and discharge of the solid electrolyte cells additionally supplied or withdrawn electrical energy or controlled by some of these means with the help of the system temperature as a signal will. 4. The method according to claim 1, characterized in that the required Air with its natural moisture content, with additional humidification Normal temperature or with the addition of steam, is used after heating. 5. The method according to claim 4, characterized in that in the Regulation of the air flow as a signal for the total voltage of the fuel cell series or the voltage between electrical connections of similar end poles of different types Fuel enamel series is used. 6. The method according to claim 1 to 4, characterized in that the Composition of fuel gas, oxidized fuel gas and resulting hydrogen / Water vapor mixture and nitrogen in the electromotive force of separate solid electrolyte cells Gas-potentiometric controlled and the regulation of the system with the help of the signals of these cells is durohführung. 7. solid electrolyte cells for DurohfUhrung the method according to claim 1, characterized in that the solid electrolyte made of zirconium oxide with any Content of hafnium oxide and from individual or mixed additions of magnesium, Calcium, soandium, yttrium oxide or oxides of the tanthamides is composed, that the electrodes are exposed to reducing gases made of porous layers of nickel, copper, Iron, cobalt or another pure, mixed or alloyed metal phase with mixed in anti-sintering agents such as Zirconium oxide as an addition of 5 - 50 parts; exist or that between Solid electrolyte and electrode are placed in a layer consisting of 30 to 80 mol% Chromium, cerium or uranium oxide plus 10 to 55 mol% zirconium oxide plus 10 to 15 mol% yttrium, Magnesium or other solid electrolyte additive oxide. 8. Vorriohtung for performing the method according to Anspruoh 1 thereby characterized in that the connections between the individual solid electrolyte cells as well as between cell series on different solid electrolyte tubes with the help of the solid electrolyte wall is guided and fused in gas-tight with a glass Metal wires, mixed metal-ceramic bodies or ceramic pins made of material from for the electrodes are made under oxidizing gas type used. 9. Device for carrying out the method according to claim 1 and 8, characterized in that in groups of series from Brenastofi- and electrolysis cells Similar end poles of the fuel cell series are conductively connected to one another and are led out of the system by these lines.